This invention relates to footwear of the kind adapted to have ground-engaging studs releasably attached to it. Footwear of that kind is often worn by people pursuing sports or games. The studs are generally intended to improve the grip of the footwear on the ground, and they may be of a wide variety of shapes. They may, for example be relatively blunt, with flat or rounded ends or more sharp, like spikes. For convenience of description, however, they will hereinafter be referred to generically as studs.
Detachable and replaceable studs are usually provided with spigots which are formed with external screw-threads. Each spigot can be screwed into a socket, in the underside of an article of footwear, formed with an internal screw-thread of complementary form.
Studs and sockets of those kinds are described and illustrated in the specifications of British patents Nos. 1 564 903, 2 028 102, 2 163 037, 2 115 683, 2 191 079 and British patent application No. 8805473 (publication No. 2 202 916A).
An object of the present invention is to provide an improved form of stud and socket.
From a first aspect the present invention consists in a combination of a stud and a socket for studded footwear in which the socket is formed with an internal screw-thread for receiving an externally screw-threaded spigot on the stud and in which the stud and socket have radially facing locking formations operative to come into mutual engagement when the spigot has been screwed into the socket to a predetermined axial position so as to impede the spigot from being screwed any further into the socket and to afford resistance to unscrewing, the stud and socket being fully assembled when the spigot is in said predetermined axial position, the arrangement being such that the stud can be unscrewed from the fully assembled position when a predetermined torque is applied to the spigot, at least one of the locking formations yielding resiliently to permit that unscrewing to occur.
The screw-threads on the stud and socket may comprise buttress threads. The screw-threads may be single-start threads but are preferably multi-start threads, a two-start thread being particularly preferred. The arrangement is preferably such, when a multi-start thread is employed, that the stud can be screwed into a fully assembled position whichever one of the thread starts on the stud comes into engagement with any selected one of the thread starts in the socket. The screw-threads on the stud and socket, whether single-start or multi-start, are preferably such that from an initial position, in which the threads are about to overlap each other, to the fully installed position (or to a fully installed position) the stud is rotated relatively to the socket through a total angle which is no more than one and a half full turns (540.degree.) and no less than three quarters of a full turn (270.degree.); the total angle is preferably no more than one and a quarter full turns (450.degree.) and is most preferably about a full turn (360.degree.).
Relative to the screw axis, the locking formations preferably comprise an outer locking formation on the socket and a complementary inner locking formation on the stud. In a preferred construction, the inner locking formation faces radially outwards from a ring constituting part of the stud and spaced radially outwards from the spigot, and the outer locking formation faces radially inwards from an outer ring constituting part of the socket and spaced radially outwards from an inner ring of the socket bounding its internal screw thread; in assembling the stud and socket the stud ring becomes inserted into an annular space between the inner and outer rings of the socket. The outer locking formation may be so constituted as to be situated at a single location or may be so constituted as to be situated at two or more spaced locations. Similarly the inner locking formation may be so constituted as to be situated at a single location or may be so constituted as to be situated at two or more spaced locations.
Preferably one of said inner and outer locking formations comprises at least one projection while the other of said locking formations provides at least one recess (for receiving the projection, or an associated one of the projections) and stop means operative to engage the projection immediately beyond the recess so as to prevent the spigot being screwed any further into the socket. Preferably it is the inner locking formation, on the stud, which consists of or includes the projection or projections.
From a second aspect the present invention consists in a stud for use in a combination in accordance with the first aspect of the present invention.
From a third aspect the present invention consists in a socket for use in a combination in accordance with the first aspect of the present invention.
From a fourth aspect the present invention consists in an article of footwear incorporating at least one socket in accordance with the third aspect of the present invention.
An embodiment of the present invention is illustrated, by way of example, in the accompanying drawings.